The present invention relates to a methylated acidulated soybean soapstock herbicidal adjuvant as well as a process for making the adjuvant, a herbicidal mixture that includes the adjuvant and a method for boosting herbicide performance.
Acidulated soybean soapstock is a waste product of soybean processing. The acidulated soybean soapstock is known as "foots" because the soapstock settles at the bottom of a tank collecting waste products from soybean oil processing. The term "foots" also connotes a historic non-utility of the product.
Acidulated soybean soapstock has had only a very limited utility because the acidulated soapstock includes water and impurities as well as some free fatty acids and neutral oil. These materials are not compatible with each other and interfere in extraction processes.
Acidulated soybean soapstock has been utilized as an ingredient in animal feed. In particular, the acidulated soybean soapstock has been used in feed for chickens, hogs, carp, and cockerels.
Acidulated soybean soapstock has also been described as an ingredient of a herbicidal mixture. The Gednalske et al. Patent, U.S. Pat. No. 5,260,260, issued Nov. 9, 1993, describes a mixture that includes acidulated soybean soapstock along with a number of specific herbicides in order to boost the performance of the herbicides.
Although acidulated soybean soapstock has had only limited usefulness, in general, lower alcohol esters of fatty acids have many industrial uses. Methyl and ethyl esters of fatty acids are gaining in importance for use as additives and substitutes to diesel fuel as well as for production of surface active agents and alcohol.
Fatty acid esters of lower alcohols are typically prepared by a transesterification reaction of neutral glycerides using alkaline catalysts such as described in the patents of Bradshaw, U.S. Pat. No. 2,271,619 and Meuly, U.S. Pat. No. 2,360,844. A direct esterification of fatty acids with methanol in a vapor phase using KHSO.sub.4 has been described in Ruhrchemie, A. G., British Patent 957,679, issued May 15, 1964.
A use of potassium hydrogen sulfate, ammonium hydrogen sulfate and sulfonated ion exchange resin for the pre-esterification of fats and oils generally has been described by Y. M. Choo, K. Y. Cheah, A. N. Ma and A. Halim in Proceedings of World Conf. (1990) at 292-295. A process for a pre-esterification of free fatty acids in fats and oils using ion exchange resins has been described in U.S. Pat. No. 4,698,186, issued Oct. 6, 1987.
A combination of sulfuric acid and sulfonic acid has been described for esterification of fatty acids and glycerides using ethanol containing 7 to 30% by weight of water in U.S. Pat. No. 4,695,411, issued Sep. 22, 1987. A preparation of esters by esterification of fatty acids or glycerides with alcohols using an enzyme as a catalyst has been described in U.S. Pat. No. 4,956,286, issued Sep. 11, 1990.
The Kawahara et al. patent, U.S. Pat. No. 4,164,506, issued Aug. 14, 1979, describes production of lower alcohol esters of fatty acids by esterifying free fatty acids of unrefined fats having an acid value of 7.7 with a lower alcohol in an amount greater than the alcohol's solubility in the fats in a presence of an acid catalyst to make a product mixture. The product mixture is separated into a fat layer and a lower alcohol layer that may be removed. The fat layer is then subjected to an interesterification reaction between the resulting refined fat and a lower alcohol in the presence of an alkaline catalyst.